HUMAN PHYSIOLOGY Objectives: 1.Define homeostasis 2.Describe mechanisms used by the human body to maintain balance 3.Identify how the body uses these mechanisms to maintain homeostasis

HOMEOSTASIS Tendency towards a relatively stable state or equilibrium (balance) Examples: Body Temperature 98.6 F Blood has a neutral pH = 7

Mechanisms Use to Maintain Homeostasis 1.Electro-chemical signals  quick messages transferred by the nervous system 2.Negative feedback mechanisms  long term responses often carried out by hormones 3.Lock and Key  controls transmission of messages based on a shape configuration at the cellular level

Negative Feedback Mechanisms Any change from the normal range of function is opposed or resisted Two responses that work in opposition Examples: Blood pressure Temperature Respiration rate Blood glucose levels

Negative Feedback and Blood Sugar

Lock and Key Model Defined Molecules have a shape that only fits specific receptors Ex. Square peg only fits into square hole, star peg only fits into star hole Enzymes  chemical proteins in the body that assist or speed up chemical reactions (catalyst) hill.com/sites/ / student_view0/chapter2/an imation__how_enzymes_w ork.html

Communication Cells communicate with one another by releasing chemicals. These chemicals bind to receptors on the surface of other cells The chemicals may be delivered to nearby cells or cells across the body (using the blood stream) When the lock and key is formed, the message has been sent

Determining “Self” from Invaders Your bodies immune (defense) system needs to be able to determine what is “self” and what is an invader It uses the lock and key method to determine invaders from self

Using Lock and Key Model in Therapies Scientists create drugs that mimic (look like) messenger molecules These messenger molecules may activate the response Or the molecule may fit, but not perfectly, so the hole is blocked and the message CANNOT be sent